Chemometric evaluation of nine alcohol biomarkers in a large population of clinically-classified subjects: pre-eminence of ethyl glucuronide concentration in hair for confirmatory classification.

An important goal of forensic and clinical toxicology is to identify biological markers of ethanol consumption that allow an objective diagnosis of chronic alcohol misuse. Blood and head hair samples were collected from 175 subjects-objectively classified as non-drinkers (N=65), social drinkers (N=51) and active heavy drinkers (N=59)-and analyzed to determine eight traditional indirect biomarkers of ethanol consumption [aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyltransferase (γ-GT), alkaline phosphatase (ALP), mean corpuscular volume (MCV), carbohydrate-deficient transferrin (CDT), and cholesterol and triglycerides in blood] and one direct biomarker [ethyl glucuronide (EtG) in head hair]. The experimental values obtained from these determinations were submitted to statistical evaluations. In particular, Kruskal-Wallis, Mann-Whitney and ROC curve analyses, together with principal component analysis (PCA), allowed the diagnostic performances of the various biomarkers to be evaluated and compared consistently. From these evaluations, it was possible to deduce that EtG measured in head hair is the only biomarker that can conclusively discriminate active heavy drinkers from social and non-drinkers, using a cut-off value of 30 pg/mg. In contrast, a few indirect biomarkers such as ALP, cholesterol, and triglycerides showed extremely low diagnostic abilities and may convey misleading information. AST and ALT proved to be highly correlated and exhibited quite low sensitivity and specificity. Consequently, either of these parameters can be discarded without compromising the classification efficiency. Among the indirect biomarkers, γ-GT provided the highest diagnostic accuracy, while CDT and MCV yielded high specificity but low sensitivity. It was therefore concluded that EtG in head hair is the only biomarker capable of supporting a confirmatory diagnosis of chronic alcohol abuse in both forensic and clinical practice, while it was found that γ-GT, CDT, MCV, and AST--whether used alone or in combination--do not allow the conclusive classification of subjects according to ethanol consumption. However, a diagnostic strategy combining these four parameters could be formulated in order to create a multivariate model capable of screening suspected active heavy drinkers.